Transformer



Aug. 6, 1929- L. H. BURNHAM 1,723,340

TRANSFORMER Filed Dec. 14, 1928 Fi .l. Fi .2. 3% j g 1 Inventor": Loc ks H fiurnham,

His Attorney;

Patented Aug. 6, 1929.

UNITED STATES PATENT OFFICE.

LOCKE H. BURNHAH, 01' PITTSFIELD, HASSACHUSETTS, ASSIGNOB TO GENERAL ELIG- TBIO COMPANY, A OOBPORATION OF NEW YORK.

'rmsroma.

Application Med December 14, 1928. Serial 1h. 325,888.

My invention relates to transformers. The maximum load which a transformer can carry is generally limited by the temperature of the hottest art of the windings. The load capacity is t erefone usually increased by rmitting or causing currents of some coo in medium such as oil or air to flow throug ventilating ducts and passages in the windings. It is obvious that if some part of the windin is heated more than the rest of the trans ormer, then the load capacity of the whole transformer will be limited by the tem rature of this hottest part. The general ject of the invention I5 13 to provide an improved winding arrangement wherein the temperatures may be more nearly uniform throughout.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 is a sectionalview of an air blast transformer with a low voltage winding constructed in accordance with the invention, the view being on line 11v of Fig. 2; Fi 2 is a sectional view .on the line 2-2 0% Fig. 1; Fig. 3 is a perspective view on a reduced scale of a section of the low voltage winding shown in Figs. 1 and 2, and Fig. 4 shows a modified construction of a low voltage winding section.

Like reference characters indicate similar parts in the different figures of the drawing.

The transformer shown in the drawing is a horizontal core air blast t transformer. The magnetic core 10 as three legs, the. center le being surrounded by three sections 11 of a low volt e winding and two sections 12 of a high vo tage winding. The core 10 with its windings is supported on a closed hollowbase 13 into which air may be forced to provide a source of air under ressure from which the air will flow upwar l and transversely to the winding leg of thecore through ventilating spaces between the winding coils and in the core to cool both.

The small portions of the windings immediately above the center le of the core are of course considerably shie ded from the cooling air currents by this core leg and the insulation between it and the windings. These shielded arts of the. windings are therefore less e eetively cooled than the other parts which are not shielded and are ventilating passages for conducting a cooling medium transversely of said winding winding being of readily reached by the air. may not be serious in the case of the winding sections 12 because these form the high voltage winding'and carry only a small current. The winding sections 11, however, operate at low voltage and carry very heavy current so that the heating effect is much greater.

The heavy current winding sections 11 are formed from straight flat conductive strips, preferably copper, as shown in 3, the strips being welded together at the joints near the corners of the winding. In the form shown in Fig. 3, the strips 14 which areshielded from the air currents by the core are substantially wider and therefore have greater cross section andless resistance than the other strips which form the rest of the winding. The heating effect of the curv rent is thus less in the strips 14 than in the other parts of the winding so that the tem'-' perature may be about the samethroughout the winding even though the cooling effect of the-air is-not.

A low voltage winding 11 built up in a different way is shown in Fig. 4. The wider part of each turn includes a strip 15 similar to the other parts of the winding and a narrow strip 16', the strips 15 and 16 being welded together to form a single wide strip similar to the stri 14 of Figs. 1 to 3.

The invention as been explained by describing and illustrating particular forms thereof but it will be apparent that various changes may be made without depart' from the scope of the invention as defin dd in the ap ended claims.

What claim as new and desire to secure by Letters Patent of the United States, is:

1. A transfiormer including a magnetic core ha'ving a winding leg, and a winding surrounding said winding leg and having leg, whereby a portion of said winding is shielded from said cooling medium by the winding leg, said shielded portion of the greater cross section than other unshiel portions.

2. An air blast transformer including a magnetic core having a windin leg, and a winding surrounding said win mg leg and having ventilating passages for conduct' cooling currents of air transversely ofwinding leg, whereby a portion of said winding is shielded from said air currents by the winding leg, said shielded portion of the u.

bein of greater cross section than under pressure, whereby a portion of said winding at the opposite side of said winding leg from said source of air is shielded from the cooling" currents of air, said shielded portion of the winding being of 15 greater cross section than other unshielded portions thereof.

In witness whereof, I have hereunto set my hand this 12th da of December 1928.

' Loo H. BURNHAM. 

